Visible stuttering in AES encrypted playlist about flashls HOT 12 CLOSED

ok I can see some glitch around t=10s while staying on the lowest level (using http://vhx-uploads-development.s3.amazonaws.com/charlietran/videos/8197/39380/200-dKzMBrZyBbxg-AetqyFD.m3u8 )

also other glitches are visible later on, around fragment boundaries.
this is not a regression from c0284ea, and this is not happening on IOS.

I am suspecting the following could give some clue on the root cause:
DEBUG:TS: partial AVC PES at end of segment

from flashls.

I confirm the issue is not linked to AES decryption.
I decrypted the playlist on my machine using a special tool and I got the same glitches while playing back the decrypted playlist.
then I tried concatenating all decrypted fragments into one unique fragment and played it back with flashls, issue is gone.
=> glitch should be related to reassembly issue of video PES packets splitted accross fragments. this case should be handled already but might be buggy.
Cheers,
Mangui

from flashls.

Thanks so much for confirming that, where in Flashls are split PES packets handled? I'll try to dig in deeper and look for the bug.

from flashls.

it is happening in TSDemuxer.as
I found the root cause. there are some AVC NAL Unit overlapping between segments.
basically when parsing the first AVC PES of second fragment, I can see some overflows. it means that first AVC PES of second fragment contains the end of the last NAL Unit of first fragment.

this is checked here : https://github.com/mangui/flashls/blob/master/src/org/mangui/hls/demux/TSDemuxer.as#L300-L304
but last video tag is null at that time, as the demux is reinstanciated between fragments.

I am reviewing the demuxer logic to be able to handle such kind of case.
Cheers,
Mangui

from flashls.

Hi @charlietran, you might recheck your stream with flashls/master

from flashls.

this should work fine when staying on same level, but there are still issues when switching levels.

from flashls.

also there is still an audio glitch while staying on same level
basically my commit just fix the video glitch while staying on same level

from flashls.

audio glitch issue should be fixed now.
some issues are remaining when seeking/switching level. i am checking what is going on

from flashls.

Hi @charlietran
seeking should work fine now. however there are still video glitches when switching levels. but i dont think this could be fixed.
if a video frame is splitted across two segments and level switching is occuring, there will anyway be artifacts or video frame loss.

but now, flashls should be more robust to bad segmentation when staying on same level.
Cheers,
Mangui

from flashls.

amazing, thanks @mangui! is there any way to prevent video frames being
split? the way I'm segmenting right now is every 10s with keyframes every
2s, which i figured would prevent frames from being split like this.

On Thu, Jul 31, 2014 at 12:56 PM, Guillaume du Pontavice <
[email protected]> wrote:

Hi @charlietran https://github.com/charlietran
seeking should work fine now. however there are still video glitches when
switching levels. but i dont think this could be fixed.
if a video frame is splitted across two segments and level switching is
occuring, there will anyway be artifacts or video frame loss.

but now, flashls should be more robust to bad segmentation when staying on
same level.
Cheers,
Mangui

—
Reply to this email directly or view it on GitHub
#31 (comment).

from flashls.

you need to use a good segmenter ... yours seems broken.
on my side I use ffmpeg internal segmenter. it works quite well.

from flashls.

Closing this, the fixes have made streaming MUCH better. We'll look into our segmenter, thanks again.

from flashls.